linux-kernel - Re: [PATCH][GIT PULL] tracing: Fix compile issue for trace_sched

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Fri, 22 Oct 2010 16:23:02 +0200
From:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
To:	Jason Baron <jbaron@...hat.com>
Cc:	Ingo Molnar <mingo@...e.hu>, Steven Rostedt <rostedt@...dmis.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	"H. Peter Anvin" <hpa@...or.com>,
	Arnaldo Carvalho de Melo <acme@...hat.com>, tj@...nel.org
Subject: Re: [PATCH][GIT PULL] tracing: Fix compile issue for
 trace_sched_wakeup.c

On Fri, 2010-10-22 at 10:13 -0400, Jason Baron wrote:
> On Fri, Oct 22, 2010 at 10:14:31AM +0200, Peter Zijlstra wrote:
> > On Thu, 2010-10-21 at 21:44 -0400, Jason Baron wrote:
> > 
> > > I finally found that we actually continue to run after the above
> > > apparent 'hang'. That is, we continue to make progress updating the jump
> > > labels. And doing a dump of all the system tasks at the time of the hang
> > > showed the processes in various places besides the stop machine threads.
> > > Thus, I thought that perhaps, for some reason the stop machine threads
> > > weren't being scheduled.
> > > 
> > > Thus, I tried commenting out the special scheduling that is set up for
> > > stop machine threads, and that fixed the hang. I haven't yet looked into
> > > what might be going wrong with that scheduling...but maybe somebody else
> > > knows...
> > 
> > Hrmm, so are you saying rq->stop was runnable but not running?
> 
> yes, that's what it seems like.
> 
> > 
> > That would imply broken wakeup-preemption, does something like the below
> > cure that?
> > 
> > 
> 
> no still seeing the same hang with the below patch...also, as a data point I
> backed out the patch that adds the stop_sched_class and that resolved the hang
> as well - just as a data point.

Weird... and there's no hotplugging happening, right?

Can this be reproduced in qemu? I don't have a i386-smp machine around
to use.

Could you trace the thing with all sched (except the sched_stat)
tracepoints enabled? I think there's a sysrq key to dump the trace once
the machine's stuck.. 

Hopefully that disables ftrace before it starts dumping otherwise the
dump is useless -- Steven?

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/